Many rheological instruments have been too complex and too expensive to meet the full needs of industrial process users and laboratory users. Also, past designs have not been adaptable to the variety of tests required by users, thereby forcing the purchase of several pieces of equipment, impracticably expensive equipment, or limitations in testing capability.
The state of the art of more affordable viscometry involves a calibrated application of shear force to a fluid to be tested and measuring torque and/or time-to-torque of the shear resistance of the fluid (its viscosity). Standard Scanning Brookfield techniques are well known in the field of viscometry and rheology. See, e.g., ASTM D 5133-96; See also, e.g., prior U.S. Pat. No. 3,886,789 (Jun. 3, 1975) of Donald W. Brookfield and U.S. Pat. No. 4,175,425 (Nov. 27, 1979) and U.S. Pat. No. 5,167,143 (Dec. 1, 1992) of David A. Brookfield, all of common assignment with the present application and the contents of which are incorporated by reference as though spelled out at length herein. See also the references cited in said prior patents.
There are many materials whose viscosity changes during processes of thermo-reversible gelation or chemical gelation (chemical cross-linking.) Such materials include, for example, gelatin, curable epoxies, certain lubricants, and mixtures of synthetic polymers and solvents. When such materials undergo state changes, their viscosities can change up to four or five decades (orders of magnitude.) Generic gel timers provide no viscosity data to laboratory personnel. Such personnel who wish to acquire viscosity data throughout the entire gelation process are required to conduct numerous separate measurements requiring careful process parameter definitions.
Thus, it would be useful to provide affordable instrumentation and a method for automatically measuring multiple decades of apparent viscosity changes in a material as it undergoes a state change such as occurs in thermo-reversible gelation or chemical gelation.